Stirrer



G. A. STAAF Jan. 6, 1970 STIRRER 1 2 Sheets-Sheet 1 Filed April 12, 1968 Fig. 1

Jan. 6, 1970 a. A. STAAF 3,483,033

STIRRER Filed April 12, 1968 2 Sheets-Sheet 2 United States Patent Offi ce 3,488,038 Patented Jan. 6, 1970 3,488,038 STIRRER Gustaf Adolf Staaf, Navlgatorsgatan 6, Vasteras, Sweden Filed Apr. 12, 1968, Ser. No. 720,907 Claims priority, application Sweden, Apr. 25, 1967,

Int. ci. non 7/22 US. Cl. 416-188 4 Claims ABSTRACT OF THE DISCLOSURE A stirrer includes a rotating shaft having an axial-flow type propeller secured thereto. A flow-guiding body is carried by the shaft downstream of the propeller and is interconnected with the shaft to transfer axial forces to the shaft opposing the'force of reaction of the propeller to reduce the axial thrust to be carried by an associated shaft bearing.

of a radial-flow turbine stirrer.

The present invention has for its object to provide for such improvements in a stirrer comprising an impeller in the form of a propeller as to minimize the thrust or compressive forces to which the impeller shaft is subjected in operation to thereby reduce the cost of manufacture of the impellershaft and, its bearing means.

For the object stated, according to the invention, a stirrer for liquid fluids comprising: an axial-flow propeller secured to a rotary shaft is mainly characterized in that the impeller shaft carries at the downstream side of the propeller a flow-guiding body adapted to divert the initially axial liquid flow radially -.away from the shaft. thereby causing the propeller shaft to be subjected-in addition to a resultant axially directed force of reaction from the propeller-also to an qppositely directed force of reaction from said flow-guiding body, thereby reducing the axial thrust to be carried by the shaft-bearing means. I

The invention will now be described more in detail with reference to the accompanying drawings, in which:

FIGURE 1, in a vertical cross-sectional view, illustrates a preferred embodiment thereof;

FIGURE 2, on a larger scale, shows the bottom-end portion of the stirrer shaft carrying the propeller and v flow-guiding body; and

thereof. Beneath the propeller there is secured to this shaft, in accordance with the present invention, a flowguiding body 19. This flow guide 19 is shaped as a body of revolution having a concavely curved generatrix and serves for diverting in a radially outward direction the vertically downward-directed liquid flow from the propeller. Mounted on the interior surface of the side wall of the container 11 are a plurality of suppressor vanes 20 projecting radially inward in vertical planes, respectively.

During rotation of the stirrer propeller 18, the latter,

in cooperation with the flow guide 19 rotating together therewith, will cause the liquid to flow along paths as indicated by the arrows. The propeller will'also impart to the liquid a rotational flow circumferentially within the container. The suppressor vanes 20, however, will be effective to reduce such circumferential flow whereby no harmful vortex formation will take plac'earound the propeller shaft.

The forces created during rotation of the stirrer are illustrated in FIGURE 2. The blades of the -propeller 18 are subjected to upwardly directed forces of reaction 22, which may be added to each other to form an upwardly directed resultant force 23 along the central axis of the shaft. The initially vertical fluid flow will be diverted by the flow guide 19 into radial directions, as indicated by arrows 21, and as a result of this the flow guide will be subjected to forces of reaction having downwardly directed components 24 the resultant sum of-which, 25,

will act downwardly along the central axis of the shaft.

. The resultant force to which the shaft is subjected will be upwardly directed and constituted by the force 23 less the force 25.

The components of the forces of reaction acting on the flow guide 19 which are directed at right: angles to the shaft will tend to stabilize and to damp any lateral oscillations of the stirrer shaft 17 tending to occur in operation. A further improved damping. action against oscillations will be attained if the flow-guiding body is made in the form of a downwardly open-ended hollow body which is filled with liquid, in which case the relatively large mass of such liquid will also have to be set in oscillatory motion when oscillations tend to 'occur.

The flow-guiding body 19 need not necessarily provide a continuously curved guiding. surface for the liquid flow. As shown in FIGURE 3, the flow guide 19. is composed of a plurality of truncated cones 26, 27, 28 and a circular disc 29 projecting radially relative to the shaft. FIGURE 4 shows a flow guide 19 which is composed of one truncated cone 30 and a circular end disc 31. The flow guide need not rotate together with the shaft but could instead be carried rotatably by the same.

What I claim is: p

1. A stirrer for liquids comprising a rotary operating shaft, an axial-flow type propeller secured to such shaft, a flow-guiding body carried by said shaft at the downstream side of the propeller andbeing adapted to divert the initially axial liquid flow radially away from the shaft. said flow-guiding body being interconnected with said shaft to transfer axially directed forces thereto thereby causing the shaft to be subjected to aforce of reaction from said flow-guiding body which is oppositely directed to the axially directed force of reaction from the propeller to thereby reduce the axial thrust to be carried by an associated shaft-bearing means.

2. A stirrer for liquid fluids according to claim 1, char- 3 acterized in that said flow-guiding body is rigidly con- References Cited nected to the impeller shaft so as to partake in the ro- UNITED STATES PATENTS tation of said shaft.

s. A stirrer for liquid fluids according to claim 1, char- 3413i: gf f g 3251 3? acterized in that said flow-guiding body is constituted by 5 421191 5/1947 Durdig a body of revolution having a continuously concavely 2:464:588 3/1949 curved generatrix.

4. A stirrer for liquid fluids according to claim 1, char- ROBERT JENKINS, Primary Examiner acterized in that said flow-guiding body is composed of a number of truncated cones and a circular disc extend- 10 U.S. Cl. X.R, ing at right angles to the shaft. 259-108 

